Agriochoerus latifrons, Ectocion ralstonensis, Megaladapis, Maganadapis and Adapis

Megaladapis insignis (Forsyth Major 1894, up to 1.5m in length) is the extinct koala lemur from Madagascar. The arms were longer than the legs. The snout remains unknown. Only three molars were present. Here it nests between Notharctus and the rest of the primates, but clearly has been evolving its koala-like shape for the entire Cenozoic.

Agriochoerus latifrons and Ectocion ralstonensis

Agriochoerus latifrons (Leidy 1850, 1869; Wortman 1895, O'Harra 1920, Late Eocene to Oligocene, 38–16mya) is known as the artiodactyl with thumbs. It has a tooth pattern with large lateral upper canines followed by a diastema. The lower canines align behind the uppers during occlusion, which is different from most synapsids. In the LRT, this taxon is the basalmost artiodactyl. Agriochoerus has slender, vestigial thumbs. Smaller Ectocion ralstonensis appears to be a juvenile of this genus and species.

Ectocion ralstonensis (Cope 1882 a, e, Granger 1915; Late Paleocene; 11 cm skull length) is generally considered a member of the Phenacodontidae, like Phenacodus, but here nests It nests close to Agriochoerus latifrons, perhaps as a juvenile given its small size, large orbit and short rostrum.

Adapis parisiensis (Cuvier 1821, Gingerich 1975, Eocene, 40mya; size) nests between Notharctus and Mandrill in the LRT. So, it is in the human lineage. Note the forward-facing eyes, smaller rostrum, larger canines, upturned premaxilla making room for large lower canines and incisors.

Magnadapis quercyi (Godinot and Couette 2008, MNHN QU 10875 Late Eocene, 11cm skull length) is a sister to Adapis in the LRT.

Cuvier GB 1822. Recherches sur les ossemens fossiles 3:265.

Gingerich PD 1975. Dentition of Adapis parisiensis and the evolution of lemuriform primates in I. Tattersall et al. (eds.), Lemur Biology. Plenum Press, NY.

Gingerich PD 1981. Cranial morphology and adaptations in Eocene Adapidae. I. Sexual dimorphism in Adapis magnus and Adapis parisiensis.

Gingerich PD and Martin RD 1981. Cranial morphology and adaptations in Eocene Adapidae. II. The Cambridge skull of Adapis parisiensis. American Journal of Physical Anthropology. 56 (3): 235–257. doi:10.1002/ajpa.1330560304

Godinot M and Couette S 2008. Morphological diversity in the skulls of large adapines (Primates, Adapiformes) and its systematic implications. in E. J. Sargis and M. Dagosto (eds.), Mammalian Evolutionary Morphology: A Tribute to Frederick Szalay .

Leidy J 1850. [Abstract of remarks made before a meeting of the Academy of Natural Sciences of Philadelphia, December 17th, 1850]. Proceedings of the Academy of Natural Sciences of Philadelphia 5(1):121-122.

Leidy J 1869. Extinct Mammals of Dakota and Nebraska:Including an account of some allied forms from other localities, together with a synopsis of the mammalian remains of North America., Journal of the Academy of Natural Sciences, Philadelphia 2(7): 135–141.

Major CIF 1894. On Megaladapis madagascariensis, an Extinct Gigantic Lemuroid from Madagascar; with Remarks on the Associated Fauna, and on Its Geological Age. Philosophical Transactions of the Royal Society B: Biological Sciences. 185: 15–38.

Major CIF 1900. Extinct Mammalia from Madagascar. I. Megaladapis insignis, sp. N. Philosophical Transactions of the Royal Society B: Biological Sciences. 193 (185–193): 47–50.

O'Harra CC 1920. The White River Badlands. South Dakota School of Mines. 13: 1–181 + plates.

Wortman JL 1895. On the osteology of Agriochoerus. Bulletin of the American Museum of Natural History 7(4):145–179.

wiki/Adapis
wiki/Magnadapis
wiki/Megaladapis
wiki/Agriochoerus
wiki/Ectocion